Mammals
Sperm Whale
Physeter macrocephalus · also called cachalot, great sperm whale
The sperm whale is a creature of superlatives — the largest toothed predator that has ever lived, the owner of the biggest brain on Earth, the deepest-diving whale, and the loudest animal. It spends its life plunging into the black depths of the open ocean to hunt squid by sound.
Overview
Sperm whales live in deep water in every ocean, from tropical seas to the fringe of the polar ice. Their society is split by sex: females and their young form stable, cooperative units of about ten animals in warmer waters, with several units forming larger “clans” that share a dialect of clicks, while mature males live alone or in loose groups and travel to high latitudes to feed, returning to the tropics only to breed.
The great head
Up to a third of a sperm whale’s length is head, and almost all of it is a sound system. The spermaceti organ and the fibrous “junk” below it are reservoirs of waxy oil that focus and beam the whale’s clicks. Air driven through valves near the blowhole generates a click that reverberates through this structure and is projected forward as an intense, directional pulse. The whale reads the echoes to build a picture of the darkness ahead — the most powerful biosonar in nature, and the source of the animal’s 230-decibel clicks.
Hunting the deep
Sperm whales dive to hundreds or thousands of metres and hunt for around 45 minutes at a time, taking mostly deep-sea squid — including giant and colossal squid — along with sharks, rays, and fish. A large male eats roughly a tonne of prey a day. Their bodies are built for the pressure and the breath-hold: collapsible lungs, oxygen stored in blood and muscle, a slowed heart, and prioritised blood flow to the brain and heart.
Intelligence and society
The sperm whale’s brain is the largest of any animal, and its social life is correspondingly complex. Females share the care and even the nursing of calves, defend one another against orcas by forming a protective “marguerite” formation (heads in, tails out), and pass on culturally specific click patterns (“codas”) that mark clan membership across ocean basins.
Reproduction
Females give birth about once every four to six years after a 14–16 month pregnancy, and calves nurse for several years, sometimes many. Males mature slowly and do not compete for mates effectively until their forties. This slow life history is why the population recovers gradually.
Status
The sperm whale is listed as Vulnerable. Commercial whaling — first for spermaceti and later industrially — cut the global population by roughly two-thirds before it was protected in the 1980s. It is now slowly increasing, but faces ship strikes, entanglement in fishing gear, ingestion of plastic and marine debris, chemical pollution that concentrates in its blubber, and underwater noise that interferes with the sonar it depends on to feed.
Sperm Whale: common questions
Why does the sperm whale have such a huge head?
The front third of a sperm whale is a giant sound-production system. It contains the spermaceti organ and the "junk" — chambers of waxy oil and connective tissue — plus the "monkey lips," a valve near the blowhole. Air forced through the monkey lips makes a click, which bounces off an air sac at the back of the skull, is focused forward through the oil-filled head, and leaves as a tightly aimed beam. The whale uses these clicks as biosonar to find squid in total darkness, and the loudest clicks may even stun prey. This acoustic machinery is why the head is so enormous.
How deep can a sperm whale dive?
Sperm whales are among the deepest-diving mammals. Typical foraging dives reach 400 to 1,200 metres and last around 45 minutes, and individuals have been recorded below 2,000 metres and staying down for over 90 minutes. They cope with the pressure by collapsing their lungs, storing oxygen in muscle and blood rather than air, slowing the heart, and shutting off circulation to non-essential organs. Between dives they rest at the surface for about 8 minutes.
Do sperm whales really fight giant squid?
They eat them regularly. Giant and colossal squid are a significant food source, especially for large males, and sperm whales are often found with circular sucker scars on their heads and beaks of squid in their stomachs. Whether these are dramatic battles or the whale simply overpowering slow-moving squid in the deep is unknown — no such encounter has ever been filmed. A sperm whale eats around a tonne of squid a day.
What is spermaceti, and why were sperm whales hunted?
Spermaceti is the fine, clear-to-waxy oil that fills the whale's head — early whalers mistook it for the animal's semen, hence the name. It was prized as a lubricant, a fuel for smokeless candles and lamps, and an ingredient in cosmetics and pharmaceuticals, and it burned brighter and cleaner than any other oil available at the time. This made the sperm whale the main target of 18th- and 19th-century whaling (the era of "Moby-Dick") and again of 20th-century factory-ship whaling, which together killed hundreds of thousands.